Mismatch Compensation Research Articles

An adaptive NMPC for ROVs trajectory tracking with environmental disturbances and model uncertainties

A novel hybrid adaptive control method is presented for trajectory tracking of remotely operated underwater vehicles (ROVs) that addresses unknown disturbances and model uncertainties in this paper. Traditional nonlinear control methods struggle to handle external disturbances and uncertainty in system model. To address the trajectory tracking control needs of ROVs in complex underwater environments, a kinematic and dynamic model is first developed for a fully actuated ROV with six degrees of freedom (6-DOF). The trajectory tracking problem is formulated as an online, nonlinear receding horizon optimization process. Control increments are computed as inputs to this nonlinear optimization problem. An L1 adaptive control method (L1AC) is then developed, incorporating a state observer, adaptive control law, and time filter. The framework retains the rolling optimization process of nonlinear model predictive control (NMPC) while integrating the L1 adaptive component for instant compensation of unknown disturbances and model parameter mismatches. Numerical simulations were conducted to compare the trajectory tracking performance of the proposed hybrid adaptive method with the NMPC method under various disturbances, including ocean currents, waves, random forces, and model uncertainties. The results confirm that the proposed hybrid adaptive control scheme is more effective and robust than the standalone NMPC approach across various scenarios.

Tunable counterpropagating twin photon source

We present an optical configuration for the generation of degenerate counterpropagating photon pairs via spontaneous-parametric down-conversion in subwavelength thin waveguides with 4¯3m symmetry. The generated photon pairs exhibit orthogonal polarizations and excite TE- and TM-like modes. Compensation of the momentum mismatch between the excited modes by pump tilting enables tunable degenerate emission across the S, C, and L bands (1400 to 1600 nm). Experimental verification confirms an efficiency of ≈10−5 photon pairs per pump photon with an expected linewidth of 0.3 nm in 2-mm-long Ga0.51In0.49P waveguides. Published by the American Physical Society 2024

Government Subsidy Policies for Industrial Internet Adoption: A Tripartite Evolutionary Game Analysis

ABSTRACTUnderstanding interactions between government, platforms, and enterprises is key to developing the industrial internet ecosystem. This study constructs a tripartite evolutionary game model to analyze stakeholder interactions. We examine the equilibrium strategies of stakeholders and the asymptotic stabilities of equilibrium points through theoretical and simulation analyses. The results show that increasing the subsidy coefficient, transaction fee rates for high‐level services, and compensation for mismatches incentivize platforms to offer high‐level services. Enterprises are motivated to participate in platforms by raising joining profits and lowering transaction fees. For the government, adjusting the subsidy coefficient promotes industrial internet adoption while avoiding excessive subsidies.

Compensation of isotope ratio mismatch in double isotope dilution inductively coupled plasma mass spectrometry (ID-ICP/MS)

Abstract Exact-matching double isotope dilution inductively coupled plasma mass spectrometry (ID-ICP/MS) is widely used to characterize reference materials (RMs) in elemental analysis. In this technique, achieving exactly matching isotope ratios for the sample and calibration blends is regarded as an important prerequisite for obtaining accurate measurement results. However, meeting this condition requires multiple time-consuming iterative measurements. In the current study, an alternative approach that can avoid lengthy iterative procedures while maintaining the accuracy of the ID-ICP/MS results was successfully investigated. We examined the effects of an extensively wide range of inexact-matching isotope ratios (approximately 75%–130%) in double ID-ICP/MS for elements with a wide mass range. Our experimental study, using gravimetrically prepared samples of Ca, Cd, Cu, Fe, Hg, Mg, Ni, Pb, and Zn, demonstrated that, despite deliberately introducing mismatching of isotope ratios, the accuracy of the ID-ICP/MS results remained consistent with relative measurement bias of typically less than 0.5%. The absence of a systematic bias due to deviations in the sample blend isotope ratios from the target ratios of the calibration blends revealed that the variability due to an isotope ratio mismatch was sufficiently compensated for. Furthermore, the expanded measurement uncertainties were sufficiently small with negligible variations observed across the different matching ratios. Typically, they were less than 1%, except for Fe, Hg, Pb, and Zn which were less than 2%. This assertion is also supported by theoretically calculated error magnification factors. Consequently, it is feasible to directly utilize the marginally estimated mass fraction of the analyte of interest without extensive iterative measurements. The findings of this study provide robust data for ID-ICP/MS, allowing to circumvent lengthy iterative procedures while maintaining the accuracy and precision of the measurement results, particularly in the characterization of RMs for elemental analysis.

Robust deadbeat predictive current control for unipolar sinusoidal excited SRM with multi-parameter mismatch compensation

In the control of unipolar sinusoidal excited switched reluctance motors (SRMs), deadbeat predictive current controllers (DPCCs) have gained attention for their enhanced dynamic performance. However, periodic disturbances caused by mismatches between the predictive model’s nominal and actual system parameters degrade the control performance of SRMs. To address this issue, a robust DPCC with multi-parameter compensation is proposed to improve dq0-axes current control performance. By analyzing the impact of parameter mismatches, a Kalman filter (KF) is developed to compensate for inductance coefficient mismatches, mitigating periodic disturbances. Additionally, a disturbance estimator with measurement noise suppression is integrated into the DPCC for both state and disturbance estimation to handle residual uncertainties, including winding resistance mismatches, magnetic saturation, and unmodeled dynamics. Compared simulation and experimental results validate the effectiveness of the proposed robust DPCC.

A current-configurable charge pump with current mismatch compensation for wide output frequency range phase-locked loop

To ensure the loop stability of a wide output frequency range phase-locked loop (PLL), a current-configurable technique for a charge pump (CP) is utilized to reduce the variation of PLL phase margin within a wide frequency range. An isolation transistor is inserted into a traditional current steering CP to improve the clock accuracy and reduce degradation of the PLL lock-in speed caused by switch control signal crosstalk on the output voltage. Furthermore, a feedback-based compensation technique is developed to reduce the mismatch between the charging and discharging currents of the proposed CP, thereby improving PLL output clock accuracy. Based on these techniques, a CP circuit is designed with 0.18 μm CMOS technology and occupies an active area of 0.005 mm2. Simulation results from different process corners operated at 1.8 V show that the maximum mismatch between the charging and discharging currents of the CP decrease from 2 % to 0.6 % when the CP current is 10 μA over a temperature range from −40 ℃ to 85 ℃. The CP is used in a PLL with input and output frequencies of 25–100 MHz and 25–500 MHz, respectively. The worst phase margin of the PLL is improved from 31° to 52.3° by configuring the CP current over a range from 10 to 40 μA. The output clock accuracy of the PLL is optimized from 600 to 100 Hz/MHz under input and output frequencies of 100 and 500 MHz, respectively.

A novel IQ mismatch compensation method in wideband direct-conversion receivers.

Direct-conversion receivers (DCRs) have been widely used in recent years due to their small size and low power consumption. However, the mismatch between the in-phase (I) and the quadrature (Q) branches will seriously affect the performance of the DCRs. This paper proposes a novel blind compensation method to suppress the interference introduced by IQ mismatch. Based on the Hilbert transform, our proposed method can obtain the orthogonal signal of the I-channel signal by utilizing the Weaver architecture. Compared with traditional compensation methods, the main difference of the proposed method is that it ignores prior information, training sequences, and additional hardware circuits. Furthermore, the complexity of the proposed blind compensation method is low because no iterative operations are involved in the compensation process. The simulation results show that the proposed method has an excellent compensation performance, especially in wideband applications.

Identification and Compensation of Gain Mismatches for Whole-Angle Microhemispherical Resonator Gyroscope Based on Modal Reversal

Identification and Compensation of Gain Mismatches for Whole-Angle Microhemispherical Resonator Gyroscope Based on Modal Reversal

Model Predictive Control for water management of a two-reservoir hydroelectric power plant

In the present work, model predictive control techniques are applied to the water management of a two-reservoir hydropower plant. The availability of forecasts on water requests by the hydroelectric plant was assumed and this motivated the adoption of a model predictive control approach. Ad hoc model mismatch compensation strategies has been developed which takes into account for unknown and unmeasured water flows and model uncertainties. The MPC strategy has been designed based on first principles linear model equations and on assigned control specifications. MPC parameter tuning is suitably adapted to the occurrence of specific state conditions, thus enabling optimal management of conditions of possible reservoir overflow, limiting water wastage while ensuring prompt reaction to possible variation in water demand related to the hydropower production plan. The reliability of the proposed approach has been tested through tailored simulation experiments, taking into account different significant scenarios.

A Multi-Dimensional Calibration Based on Genetic Algorithm in a 12-Bit 750 MS/s Pipelined ADC.

As the preferred architecture for high-speed and high-resolution analog-to-digital converters (ADC), the accuracy of pipelined ADC is limited mainly by various errors arising from multiple digital-to-analog converters (MDAC). This paper presents a multi-dimensional (M-D) MDAC calibration based on a genetic algorithm (GA) in a 12-bit 750 MS/s pipelined ADC. The proposed M-D MDAC compensation model enables capacitor mismatch and static interstage gain error (IGE) compensation on the chip and prepares for subsequent background calibration based on a pseudo-random number (PN) injection to achieve accurate compensation for dynamic IGE. An M-D coefficient extraction scheme based on GA is also proposed to extract the required compensation coefficients of the foreground calibration, which avoids falling into local traps through MATLAB. The above calibration scheme has been verified in a prototype 12-bit 750 MS/s pipelined ADC. The measurement results show that the signal-to-noise and distortion ratio (SNDR) and spurious-free dynamic range (SFDR) are increased from 49.9 dB/66.7 dB to 59.6 dB/77.5 dB with the proposed calibration at 25 °C. With the help of background calibration at 85 °C, the SNDR and SFDR are improved by 3.4 dB and 8.8 dB, respectively.

An 80-Gb/s PAM-4 Simultaneous Bidirectional Transceiver With Hybrid Adaptation Scheme

This paper presents a simultaneous bidirectional (SBD) transceiver with four-level pulse amplitude modulation (PAM-4), employing a novel hybrid adaptation scheme. The possibility of extending bandwidth is explored by applying PAM-4 signaling to SBD. Furthermore, a mismatch compensation method for a hybrid circuit is proposed, which is essential for removing the outbound signal in SBD. The hybrid adaptation is easily implemented by applying the locked condition of the Mueller M|ller phase detector (MMPD) with the data level adaptation. By sharing one error sampler with MMPD and adaptation engine, the presented SBD transceiver is efficient in terms of clocking power consumption and bandwidth of a receiver front-end. A wide linear range hybrid and a data alignment technique guarantee the robust PAM-4 SBD operation. Fabricated in the 28-nm CMOS, the 80-Gb/s SBD transceiver achieves a bit error rate (BER) of less than 10-12 with an energy efficiency of 2.65 pJ/b.

Load Mismatch Compensation of Doherty Power Amplifier Using Dual-Input and Mode Reconfiguration Techniques

Doherty power amplifier (DPA) has shown great potentials in wireless communication systems. However, the output power and efficiency of a DPA are very susceptible to load mismatch. This paper presents the load mismatch analysis and compensation of coupler-based DPAs leveraging on dual-input and mode reconfiguration techniques. A comprehensive analysis, which takes voltage clipping into consideration, is conducted on a coupler-based dual-input DPA (CBDI-DPA) under load mismatch condition. It is illustrated that the parallel Doherty mode could recover the saturation and back-off drain efficiencies (DEs) for the load mismatch in the left and right half parts of the Smith chart, respectively. And the serial Doherty mode could recover the back-off and saturation DEs for the load mismatch in the left and right half parts of the Smith chart, respectively. As a validation, a CBDI-DPA operating at 2.4 GHz is fabricated and measured in this paper. Under the optimal load impedance condition, the fabricated CBDI-DPA delivers a saturation power of more than 43.5 dBm, a saturation DE of more than 70% and a 6 dB back-off DE of more than 60% in both the parallel and the serial Doherty modes. Meanwhile, the simulation and experimental results demonstrate the proposed method can recover the output power and efficiency of a DPA when the load mismatch is inside the 2:1 VSWR circle.

Incremental Model Predictive Current Control for PMSM With Online Compensation for Parameter Mismatch

Incremental Model Predictive Current Control for PMSM With Online Compensation for Parameter Mismatch

Adaptive Beamforming with Hydrophone Arrays Based on Oblique Projection in the Presence of the Steering Vector Mismatch

In sonar systems, the performance of adaptive beamformers severely degrades when mismatches occur between the actual and presumed steering vectors of the desired signal, mainly due to hydrophone position errors, amplitude-phase errors, and the scattered effect of arrays. Similarly, an inadequate number of “training” samples can lead to performance degradations similar to those caused by mismatches. In this paper, an adaptive beamforming algorithm based on oblique projection (OP-ABF) mismatch compensation is proposed to remove the degradation caused by the arbitrary-type steering vector mismatch of the desired signal. The proposed algorithm is motivated by the fact that the weight vector of adaptive beamforming can be represented as a linear combination of the optimal one and the oblique projection (OP) vector, which is generated by the steering vector mismatch and does not exist without this. Our algorithm was developed by constructing the oblique projection mismatch compensation vector (OPMCV) to provide the minimum variance distortionless response (MVDR) beamformer. Then, the algorithm could be implemented by the solution of the OP matrix with the formulation of the covariance matrix loading (CML). The simulation results of a uniform linear array (ULA) and a half-cylindrical conformal array (HCCA) show that the OP-ABF can optimize the original weight vector as much as possible without sacrificing the output signal-to-interference-plus-noise ratio (SINR) under different conditions. Experimental results for the HCCA also confirm the effectiveness of this algorithm.

A reinforcement learning‐based approach for near‐optimal sliding‐mode control of output‐constrained uncertain nonlinear systems

AbstractThis study presents a near‐optimal learning‐based approach for sliding‐mode control of uncertain nonsquare nonlinear systems subject to output constraints. To achieve a compromise between safety and optimality, a reinforcement learning algorithm is proposed to compute the near‐optimal values of the sliding manifold coefficients. In the reinforcement learning algorithm, only measured input‐output data obtained by experiments or simulations are employed. Furthermore, the presented method does not require partial knowledge of the system dynamics to initialize the reinforcement learning process. By employing the tuned sliding vector, an adaptive fuzzy sliding‐mode control (AFSMC) input, including a fuzzy term and a robust term, is generated. The fuzzy term is used to approximate an unknown nonlinear function and the robust term is designed for mismatch compensation. To guarantee that the output constraints are not violated, the adaptation laws for obtaining the fuzzy singletons and the bounds of the approximation errors are designed based on the barrier Lyapunov functions (BLF) theorem. The closed loop asymptotic stability is theoretically analyzed in the article, while the effectiveness of the method is assessed in simulation.

A 39-GHz CMOS Bidirectional Doherty Phased- Array Beamformer Using Shared-LUT DPD With Inter-Element Mismatch Compensation Technique for 5G Base Station

This article demonstrates a 39-GHz CMOS phased-array beamformer aiming for power-efficient and area-efficient fifth-generation (5G) dual-polarized multiple-in–multiple-out (DP-MIMO) applications. To address the digital pre-distortion (DPD) implementation issue in the massive beamformer elements with Doherty technique integrated, an inter-element mismatch compensation technique is introduced for improving the shared-lookup table (LUT) DPD performance over the process, voltage and temperature (PVT) variations. A bidirectional Doherty power amplifier (PA)-LNA is proposed to enhance the power back-off (PBO) efficiency regarding the high peak-to-average power ratio (PAPR) 5G signals, meanwhile cost down the system by the unbalanced neutralized bidirectional operation. The proposed phased-array beamformer chip is fabricated in 65-nm CMOS technology and packaged in a wafer-level chip-scale package (WLCSP). Each element occupies only a 0.82-mm2 chip area, including the on-chip low-dropout regulator (LDO). The measured stand-alone Doherty PA-LNA achieves 18.9-dBm saturated output power with 17.8% power-added efficiency (PAE) at 6-dB PBO in PA mode and obtains a 4.8-dB noise figure (NF) at 40 GHz in LNA mode. By utilizing the proposed mismatch compensation, the measured 64-quadrature amplitude modulation (QAM) orthogonal frequency-division multiple access (OFDMA)-mode error vector magnitude (EVM) and adjacent channel leakage ratio (ACLR) with the shared-LUT DPD are improved from −22.4 to −25.0 dB and from −28.7 to −32.1 dBc, respectively. The 64-element module achieves a 55.2-dBm saturated effective isotropic radiated power (EIRP) and supports 21-Gb/s single-carrier (SC) mode data streaming. The measured 64-element transmitter (TX) EVM is −25.2 dB at 43.2 dBm with 3.5-GSymbol/s baud rate in 64 QAM, and the corresponding 64-to-4 elements TX-to-receiver (RX) EVM is −22.5 dB. The consumed power for each element is 402 mW at saturation output point in TX mode and 87 mW in RX mode.

Capacitance-to-Digital Converter for Harvested Systems Down to 0.3 V With No Trimming, Reference, and Voltage Regulation

In this work, a capacitance-to-digital converter (CDC) suitable for direct energy harvesting is introduced. The nW peak power and the ability to operate at any supply voltage in the 0.3-1.8 V range allow complete suppression of any intermediate DC-DC conversion, and hence direct supply provision from the harvester, as demonstrated with a mm-scale solar cell. The proposed CDC architecture eliminates the need for any additional support circuitry, preserving true nW-power operation, and reducing design and integration effort. In detail, the architecture is based on a pair of double-swappable oscillators, and avoids the need for any voltage/current/frequency reference circuit in the oscillator mismatch compensation. The digital and differential nature of the architecture counteracts the effect of process/voltage/temperature variations. A load-agnostic one-time self-calibration scheme compensates mismatch, and can be run from boot to run stage of the chip lifecycle. The proposed self-calibration scheme suppresses any trimming or testing time for low-cost systems, and avoids any input capacitance disconnection requirement. A 180-nm testchip shows 7-bit ENOB down to 0.3 V and 1.37-nW total power, when powered by a 1-mm2 indoor solar cell down to 10 lux (i.e., late twilight).

Dentoalveolar compensation in various skeletal malocclusion groups in district solan population: A cephalometric study

: To assess the position and inclination of upper and lower incisors and bases in different groups of skeletal malocclusions. 45 pretreatment lateral cephalometric radiographs were included. They were divided into his three groups of skeletal class I, class II, and class III. A variety of linear and angular measurements were used to assess both the position and inclination of the maxillary and mandibular bases, incisors, and the relationship between the incisors. There was a significantly stronger correlation between anterior-posterior skeletal mismatch and maxillary alveolar bone compensation in skeletal classes I, II, and III. Except for maxillary vertical skeletal discrepancy (MP-SN) and alveolar compensation, there was a weak correlation between maxillary and mandibular vertical skeletal discrepancy and alveolar compensation. The anterior-posterior position of the skeletal jaw had a greater effect on alveolar bone changes than the vertical inclination of the skeletal jaw in the Grad variant. There may be a relationship between alveolar bone changes and skeletal anteroposterior and vertical position, inclination and intermaxillary relationship.

Reservoir Advanced Process Control for Hydroelectric Power Production

The present work is in the framework of water resource control and optimization. Specifically, an advanced process control system was designed and implemented in a hydroelectric power plant for water management. Two reservoirs (connected through a regulation gate) and a set of turbines for energy production constitute the main elements of the process. In-depth data analysis was carried out to determine the control variables and the major issues related to the previous conduction of the plant. A tailored modelization process was conducted, and satisfactory fitting performances were obtained with linear models. In particular, first-principles equations were combined with data-based techniques. The achievement of a reliable model of the plant and the availability of reliable forecasts of the measured disturbance variables—e.g., the hydroelectric power production plan—motivated the choice of a control approach based on model predictive control techniques. A tailored methodology was proposed to account for model uncertainties, and an ad hoc model mismatch compensation strategy was designed. Virtual environment simulations based on meaningful scenarios confirmed the validity of the proposed approach for reducing water waste while meeting the water demand for electric energy production. The control system was commissioned for the real plant, obtaining significant performance and a remarkable service factor.

Clinical Feasibility and Familiarization Effects of Device Delay Mismatch Compensation in Bimodal CI/HA Users.

Subjects utilizing a cochlear implant (CI) in one ear and a hearing aid (HA) on the contralateral ear suffer from mismatches in stimulation timing due to different processing latencies of both devices. This device delay mismatch leads to a temporal mismatch in auditory nerve stimulation. Compensating for this auditory nerve stimulation mismatch by compensating for the device delay mismatch can significantly improve sound source localization accuracy. One CI manufacturer has already implemented the possibility of mismatch compensation in its current fitting software. This study investigated if this fitting parameter can be readily used in clinical settings and determined the effects of familiarization to a compensated device delay mismatch over a period of 3-4 weeks. Sound localization accuracy and speech understanding in noise were measured in eleven bimodal CI/HA users, with and without a compensation of the device delay mismatch. The results showed that sound localization bias improved to 0°, implying that the localization bias towards the CI was eliminated when the device delay mismatch was compensated. The RMS error was improved by 18% with this improvement not reaching statistical significance. The effects were acute and did not further improve after 3 weeks of familiarization. For the speech tests, spatial release from masking did not improve with a compensated mismatch. The results show that this fitting parameter can be readily used by clinicians to improve sound localization ability in bimodal users. Further, our findings suggest that subjects with poor sound localization ability benefit the most from the device delay mismatch compensation.